<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>注册页面</h1>
<form action="">
    <input type="text" name="username" placeholder="用户名" onclick="fn()">
    <span></span><br>
    <input type="text" name="password" placeholder="密码">
    <input type="button" value="注册">
</form>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<script>
    function fn() {
        let data = new FormData(document.querySelector("form"));
        axios.post("/check",data).then(function (response) {
            let span = document.querySelector("span");
            span.innerText = response.data;

        })
    }
</script>
</body>
</html>